//删除一个有序链表中重复的元素
    public Node deleteDuplication() {
        Node newHead = new Node(-1);//newHead是虚拟节点，data随意设置
        Node tmp = newHead;//tmp是用来连接上一个不重复元素与下一个不重复元素的节点
        Node cur = this.head;//cur是遍历用的
        while (cur != null) {
            if (cur.next != null && cur.data == cur.next.data) {//cur.next==null会空指针异常
                while (cur.next != null && cur.data == cur.next.data) {//cur.next==null会空指针异常
                    cur = cur.next;
                }
                cur = cur.next;//多做一步循环，跳过cur.next.data(cur.data==cur.next.data).
            } else {
                while (cur.next != null) {
                    tmp.next = cur;
                    tmp = tmp.next;
                    cur = cur.next;
                }
            }
        }
        tmp.next = null;//手动置空，防止最后一个节点也重复了
        return newHead.next;//走完遍历后，tmp位置发生变化，这时只能利用newHead来返回头部结点
    }